Biomass selection and control for continuous flow granular/flocculent activated sludge processes

ABSTRACT

A continuous flow granular/flocculent sludge wastewater process selects for granule biomass capable of nitrogen and phosphorus removal and controls granule size and concentration of granular and flocculent sludge for optimal nutrient, organic, and solids removal in a smaller footprint. A series of biological process zones lead to a secondary clarifier. Mixed liquor sludge, preferably from an aerobic zone, goes through a classifier or separator processing flow from the aerobic zone, to the secondary clarifier. In a sidestream process that can be included a portion of sludge preferably from an aerobic zone goes through a classifier or separator to selectively produce a granular-rich effluent, and the clarifier may also have a separator to further concentrate granular biomass, most of which is cycled back to an initial multi-stage anaerobic process zone. The anaerobic zone is structured and operated to encourage growth of granules in subsequent process zones.

This application is a continuation-in-part of application Ser. No.16/537,379, filed Aug. 9, 2019, now U.S. Pat. No. 10,781,125, issuedSep. 22, 2020, which claimed benefit of provisional application No.62/718,313, filed Aug. 13, 2018.

BACKGROUND OF THE INVENTION

The application involves reactor process configurations and a granularsludge classifier (separator) process to control granular sludge sizeand relative fractions of granular and flocculent activated sludge in acombined continuous flow wastewater treatment system for biologicalnutrient removal.

The activated sludge process has been used since the early 1900s for thetreatment of domestic and industrial wastewater by microorganisms. Thebasic features of the traditional process are 1) mixing and aeration ofthe wastewater in a reactor with a flocculent mass containing activemicroorganisms and influent particulates, 2) a liquid/solids separationstep to separate and discharge the treated effluent from the flocculentmass, 3) wasting of excess mass produced from removal of wastewaterparticulates and biomass growth from the removal of influent substances,4) return of settled flocculent mass from an external liquid/solidsseparation step to the bioreactor or use of the settled flocculent massin the bioreactor for continuous or batch treatment of wastewater.

The process was first developed as a batch treatment process in whichthe above steps of biological contact, liquid/solids separation, andflocculent mass return are done in a single tank. Continuous flowversions of the process followed soon after and are the most commonversion used today. Continuous flow activated sludge treatment involvessingle or multiple bioreactors used in series and an externalliquid-solids separation step with recycle of the solids to thebioreactors. The process may involve the use of configurations withanaerobic, anoxic, and aerobic zones to meet treatment objectives.Gravity settling of solids in a clarifier is the most commonliquid-solids separation method. The clarifier also provides highremoval efficiency of suspended solids to produce a relatively cleareffluent low in suspended solids. Due to excess sludge production, awaste solids stream routinely removes solids from the system to controlthe bioreactor mixed liquor suspended solids (MLSS) concentration.

The traditional activated sludge process has a flocculent biomass thatin addition to consuming waste provides capture of particulate and finesolids to produce an effluent from the liquid/solids separation processthat is low total suspended solids (TSS). The flocculent biomass has avery diffused structure and a floc size commonly from 0.05-0.30 mm (FIG.1). Flocculent biomass is created by production of extracellularpolymeric substances during biomass growth which binds other bacteriaand also traps and contains colloidal and suspended particulates fromthe influent wastewater. Biomass growth in aerobic activated sludgeprocesses is the result of assimilation and oxidation of influentorganic substrate with a suitable electron acceptor such as oxygen,nitrate, or nitrite. Biomass growth can also occur from oxidation ofinorganic substrates such as ammonia, nitrite, reduced sulfur compounds,and reduced iron with a suitable electron acceptor. For the latter, thecarbon needed for biomass growth is derived from carbon dioxide.

The wastewater organic concentration is commonly measured in a batchbioassay using bacteria and is referred to as the BOD or biochemicaloxygen demand concentration. Treatment discharge standards require thatthe effluent BOD is below some specified value, typically 20 mg/L. Theeffluent BOD consists of soluble organic biodegradable substrate andbiodegradable colloidal and particulate solids. Treatment dischargestandards also require a low effluent total suspended solids (TSS) withvalues typically 20 mg/L. More stringent treatment requirements areoften required with effluent BOD and TSS concentrations 10 mg/L. Thephysical characteristics of flocculent activated sludge is effective incapturing free bacteria, and nondegraded colloidal and particulatesolids to meet permit limits for effluent TSS.

Different process tank configurations or batch treatment operation modesare also used in activated sludge processes to provide biologicalnitrogen removal and/or enhanced biological phosphorus removal (EBPR) toachieve low effluent concentrations of phosphorus and nitrogen(Tchobanoglous et al., 2014). Effluent nitrogen soluble inorganicspecies are ammonia (NH₃), nitrate (NO₃), and nitrite (NO₂). Theactivated sludge processes are designed with special configurations,including anaerobic, anoxic, and aerobic zones and operational methodsto select for bacteria with specialized metabolic capability importantfor nutrient removal. These processes include nitrification only, bothnitrification and denitrification (ND), and enhanced biologicalphosphorus removal (EBPR). Nitrification is the biological oxidation ofammonia (NH₃) to nitrite (NO₂) by one group of autotrophic bacteria andthen to nitrate (NO₃) by another group of autotrophic bacteria in thepresence of dissolved oxygen (DO). Nitrogen removal by denitrificationis done by heterotrophic bacteria that reduce NO₃/NO₂ to dinitrogen (N₂)gas during the oxidation of organic compounds in the absence of DO.Denitrification occurs in anoxic reactors. EBPR occurs in biologicaltreatment due to the growth and wasting of bacteria that store highconcentrations of phosphorus, which are referred to as phosphorusaccumulating organisms (PAOs). The growth of PAOs requires contact ofthe PAOs with influent wastewater under anaerobic conditions followed byanoxic and/or aerobic conditions. The anaerobic reactor does not receiveany significant amount of DO, NO₃ or NO₂. In the anaerobic contact zoneacetate and propionate volatile fatty acids (VFAs) from the influentwastewater or produced by organic solids fermentation in the anaerobiccontact zone are consumed by the PAOs and stored as polyhydroxyalkanoatecompounds. Stored polyphosphates in the PAOs provides energy needed bythe PAOs to take up carbon and convert to storage products. Phosphate isreleased from the PAOs to the reactor liquid during their polyphosphateuse in the anaerobic zone. The PAOs oxidize their carbon storageproducts using NO₃ or NO₂ in an anoxic zone which results in nitrogenconversion and nitrogen removal from the wastewater. PAOs oxidize theircarbon storage using oxygen in an aerobic zone. During their storedcarbon oxidation in anoxic or aerobic zones the PAOs create energy whichthey store in polyphosphate deposits by taking up phosphate from thereactor liquid. Wasting of excess PAO biomass results in phosphorusremoval from the system.

Nitrogen removal in continuous flow flocculent sludge systems have ananoxic process zone upstream of a nitrifying aerobic process zone. Theanoxic zone receives organic substrate for denitrification from influentwastewater feed or in flow from an anaerobic contact zone with PAOactivity. The anoxic reactor also receives NO₃/NO₂ in mixed liquorrecycle from the downstream aerobic nitrifying reactor. Denitrifyingbacteria oxidize the food in the anoxic reactor feed with reduction ofNO₃/NO₂ to nitrogen gas for nitrogen removal. PAOs from the EBPRanaerobic contact zone are also able to oxidize their carbon storagewith NO₃ or NO₂ in the anoxic zone to accomplish nitrogen removal.

More recently, it has been shown that activated sludge can be grown in amore compact approximate spherical self-formed biofilm layered structurein contrast to the more diffused flocculent activated sludge structure.These suspended biofilms are self-aggregating, do not require a carriermedia and are referred to as granular activated sludge. Their size maybe from 0.2 to 4.0 mm (Figdore et al., 2017). The structure of granularsludge is compared to flocculent sludge in FIG. 1. Due to the fact ofthe greater size, density, and smoother morphology, the granular sludgecan settle 5 to 30 times faster than flocculent sludge and can bethickened to a much higher concentration in a short time. A system highin granular sludge content has a 5-minute sludge volume index (SVI)approaching that of the 30-minute SVI or a SVI₅/SVI₃₀ ratio near 1.0,due to the discrete particles and fast settling. The biomassconcentration in a granular activated sludge treatment reactor can be 2to 3 times that for flocculent sludge to result in much greatertreatment ability or treatment capacity with less tank volume and lowerfootprint.

Granular biomass can be grown with ability for EBPR, nitrification, anddenitrification (Figdore et al., 2018a). The granules that contain PAOsare more versatile and, if of sufficient size, can provide simultaneousnitrification and denitrification (SND) for nitrogen removal in anaerobic zone in addition to phosphorus removal.

In contrast to flocculent sludge with its smaller and diffuse structure,granular sludge can have a layered spatial distribution of key types ofbacteria within different layers to provide unique phosphorus andnitrogen removal activity. The process configuration and classifier inthis application provides such type of granular growth due to the natureof the granular growth conditions and granular size selection. FIG. 1photomicrographs illustrate the magnitude of granule size and densityand a simple representation of the spatial distribution of bacteriainvolved in biological phosphorus and nitrogen removal. DO and NH₃ fromthe bulk liquid is taken up at the granule outer layers rich innitrifying bacteria. The NO₃ and NO₂ produced diffuses into the innercore of the granule that is rich in PAOs. The PAOs utilize the NO₃ andNO₂ for the oxidation of stored substrates with subsequent NO₃ and NO₂reduction to N₂. The soluble phosphorus in the bulk liquid is alsoremoved via diffusion and uptake by the PAOs. Due to the granule sizeall these reactions can occur in an aerated tank and thus the PAOgranules can provide simultaneous nitrification-denitrification (SND)for nitrogen removal and phosphorus removal in the same tank. Nitrogenremoval is accomplished in conventional flocculent sludge processesusing separate anoxic and aerobic reactors with internal recycle.Advantages of a granule sludge system for nutrient removal are 1) anefficient use of influent soluble BOD, also measured as solublebiodegradable chemical oxygen demand (COD), for both EBPR anddenitrification to accomplish phosphorus and nitrogen removal, and 2)denitrification in an aerobic zone which may eliminate the need for aseparate anoxic zone and internal recycle pumping for nitrogen removal.

An anaerobic contact zone with soluble food is a required processcondition to grow and sustain PAOs. When both granular sludge andflocculent sludge are recycled to an anaerobic contact zone the growthof granular sludge is inhibited. Flocculent sludge can also contain PAOsand can consume soluble biodegradable (bCOD) in the anaerobic contactzone faster than PAO-containing granular sludge because of diffusionlimitations for the large and denser granular biomass. Soluble bCOD fromthe bulk liquid must diffuse into the depth of the granules whichresults in a lower soluble BOD concentration with increasing depth.Thus, the overall rate of soluble bCOD uptake in g soluble bCOD/g VSS-his much slower for a granule than a floc because the uptake rate isproportional to the localized substrate concentration. The method inthis disclosure calls for an anaerobic first reactor contact withwastewater feed at a high soluble bCOD volumetric loading and recycle ofmostly granular biomass from the classifier as the first step, whichthus minimizes competition for food from the flocculent biomass andinstead allows more granular biomass growth and larger granules. Anothermethod using an anoxic contact zone in the same manner also favorsgrowth of granular biomass. Thus, the classifier that provides agranular sludge recycle to the high loaded first reactor works in tandemwith the first reactor to select for granular sludge growth of apreferred size and function.

A disadvantage of granular biomass is that the granular structure is notas effective as flocculent biomass in capturing colloidal and suspendedparticles contained in the wastewater. Results from a granular activatedsludge system consisting of biomass with over 90% granular sludge had anaverage effluent TSS concentration of 174 mg/L (Figdore et al., 2018b),which is well above wastewater treatment plant effluent permit TSSconcentration limits of 10-30 mg/L. Capture of colloidal and suspendedsolids by flocculent sludge and removal in liquid-solids separation isnecessary to minimize the effluent TSS concentration to meet effluentBOD and TSS treatment needs. A combined granular and flocculentactivated sludge system as describe in this disclosure can produce thenecessary effluent clarification needed to meet permit limits while alsoreducing treatment footprint requirement and providing nutrient removal.

Similar to the first flocculent activated sludge processes used, thedevelopment and application of granular activated sludge has been donewith sequencing batch reactors (SBRs). SBRs involve a batch feeding, areaction time, settling time, and effluent removal. The batch feedingtime comprises about 25% of the SBR processing time and thus multipleSBRs must be operated in synchronization or influent wastewater storageis needed.

Most biological wastewater treatment processes currently installed inthe United States and worldwide are continuous flow activated sludgeprocesses. SBRs have much different influent wastewater feedingarrangements and generally use deeper tanks than for continuous flowactivated sludge treatment systems. Process modifications that canconvert continuous flow flocculent activated sludge treatment systems toa combined granular/flocculent activated sludge system and maintain theexisting feeding and tank layout could provide many benefits includingnutrient removal and increased treatment capacity.

Most existing patents involving granular activated sludge for wastewatertreatment involve SBR technology. Others do not address the need forgrowth conditions that favor granular biomass growth with preferredtypes of bacteria over flocculent biomass growth to sustain a high levelof granular biomass in the activated sludge process and they also do notaddress the relative concentrations of granules and flocculent sludgepreferred for a combined granular/flocculent sludge process.

U.S. Pat. No. 6,566,119 relates to a sequencing batch reactor (SBR)operation producing aerobic granular activated sludge. A reactor isinoculated with aerobic microorganisms, fed a substrate under turbulentmixing conditions caused by sparging a gas containing oxygen, stoppingthe mixing for a time to allow settling of the aerobic microorganisms,and followed by removing liquid to empty the top part of the reactor andrepeating the batch feeding, aeration, settling, and effluent withdrawalcycle. The settling time is based on the height of the liquid remainingin the reactor in meters divided by a velocity of at least 5meters/hour.

U.S. Pat. No. 6,793,822 relates to an SBR operation producing aerobicbiogranules. The operation involves adding wastewater into a reactorcontaining an active biomass sludge, providing an oxygen-containing gasat a superficial upflow gas velocity greater than 0.25 cm/second toprovide oxygen for microbial uptake and to mix and suspend the biomass,initiating a period of nutrient starvation in the reactor willcontinuing to provide the oxygen-containing gas, allowing the formedaerobic granules to settle, and discharging and replacing at least aportion of the wastewater and subsequently repeating the operatingcycle. The patent claims did not specify a settling time, but thedescription specified settling times of 1 to 20 minutes. The nutrientstarvation time was estimated to be about 80% of the aeration period.

U.S. Pat. No. 7,273,553 relates to an SBR operation producing aerobicbiogranules that remove nitrogen and phosphorus compounds in addition toorganic substrates. The batch cycle consists of feeding wastewater intoa granular sludge bed in the bottom of the reactor under anaerobicconditions, aeration and mixing the reactor contents with anoxygen-containing gas, and a settling step to allow separation of theupper liquid from the activated sludge. The process descriptionspecifies that the wastewater can be introduced into the settled bedwithout fluidization of the bed or if mixing is used to contact thewastewater and settled sludge the bottom mixed volume be limited to 25%of the reactor volume. The upflow velocity during batch feeding is notgiven and a settling time of 3 min was given in a process example in thepatent description. Effluent withdrawal was given at 50% of the reactorheight in the example but no specifications on the location of theeffluent removal or effluent removal during feeding (as is now done inthe process application) was given in the claims or example. Thisprocess operation provides an environment that favors the growth ofgranules containing PAOs as described above due to the feeding ofwastewater to an anaerobic zone with settled granules and subsequentlyaerobic nitrification and denitrification reactions.

U.S. Pat. No. 8,409,440 describes another form of an SBR process usingtwo compartments and with conditions to favor growth of granular biomasswith phosphorus and nitrogen removal ability. Two reactor compartmentsthat communicate with each other at the bottom are used. Batch chargingof wastewater to the system is done by using a vacuum in the head spaceof compartment 1, which allows the intake of a batch feed withoutdisturbing a settled granular sludge bed in compartment 2. The next stepin the cycle is to open compartment 1 to atmospheric pressure, whichresults in compartment 2 receiving the batch feed from compartment 1.The feed is distributed across the reactor bottom area of compartment 2to contact and fluidize the granular bed with the wastewater underanaerobic conditions. A series of batch feedings may follow. This isthen followed by aeration and settling steps. A settling time of 5minutes before effluent decanting was given in the patent description.

Sequencing batch reactor treatment processes that accomplish biologicalnutrient removal with a granular activated sludge have been identified.However most biological treatment processes for wastewater treatment arecontinuously fed systems with external clarifiers. The continuously-fedsystems are preferred over SBR systems for moderate and larger sizeplants in view of economics, space requirements, and operationalcomplexity. Conversion of existing continuously-fed systems to SBRsystems for granular sludge selection may be difficult and noteconomically attractive in most cases in view of the arrangement of theexisting tanks and the plant piping and hydraulics. The ability toconvert existing facilities or design new facilities that developgranular activated sludge with biological nutrient removal is attractivein terms of the potential increase in plant capability and capacityprovided by the dense granular biomass.

U.S. Pat. No. 5,985,150 relates to an aerobic activated sludge reactorwith two zones and a separator in the second zone for continuous-flowtreatment with granules. Oxygen containing gas in the second zonecreates a recirculation of reactor contents between the second and firstzones with downward velocity in the first zone created by the rising gasand higher liquid elevation in the second zone. The first zone alsoreceives influent wastewater. Effluent is removed in a three-phaseseparator including release of gas released from the recirculation flowfrom the second zone to the first zone. The recirculated flow enters achamber at the top of the first zone. Water flows out of the chamber andthen upward through plate settlers at a velocity to allow the granularactivated sludge to settle back to the first zone for recirculation. Thetreated effluent exits via the plate settler. An example of the processshows an upflow velocity of 14 meter/hour in the plate separator, whichwould carry out the lighter flocculent sludge and allow granular sludgewith its higher settling velocity to be retained in the reactor.

U.S. Pat. No. 5,985,150 had no anaerobic contact zone to develop PAOgranules and granules capable of SND, and no conditions to wash outflocculent sludge, and thus high effluent total suspended solids (TSS)would be expected for treatment of domestic and industrial wastewaters.

U.S. Pat. No. 7,060,185 relates to an apparatus for treating sewageusing granulated sludge. The system has three tanks in series withrecirculating flow from the last tank to the first tank. The first tankis described as an anaerobic granulation tank, the second in series isan indirect aeration tank and the third in series is referred to as anaerobic granulation tank. The anaerobic granulation tank receives flowat the bottom of the tank made up of influent wastewater and recyclefrom the aerobic granulation tank. The recycle from the aerobicgranulation tank contains nitrate/nitrite due to the ammonia oxidationin the aerobic granulation tank. Phosphorus removing organisms containedin the granulated sludge use the recycled nitrate/nitrite for electronacceptors. The tank also contains an agitator and an upflow velocity ofliquid results in a supernatant without granules that flows to theindirect aeration tank. Oxygen is dissolved at super saturatedconditions in the indirect aeration tank. Flow from the indirectaeration tank provides dissolved oxygen for the final aerobicgranulation tank. This flow is distributed in the bottom of the aerobicgranulation tank and an agitator in the bed is also present. The upflowvelocity carries supernatant without granules with part of it beingdischarged as treated effluent and the rest as recirculation flow to theanaerobic granulation tank. The liquid upflow velocity is claimed to be1.3 to 1.7 meters/hour which would not be sufficient to suspendgranules.

U.S. Pat. No. 7,060,185 involves indirect aeration which requires muchhigher energy than that used by conventional activated sludge aerationmethods and involves a very high recycle of flow for aeration. Theadvantage claimed for the method is that it provides higher efficiencyin removing nitrogen and phosphorus due to the microorganism selection,but does not claim to provide a higher biomass concentration in thereactors due to granular growth to increase reactor capacity. It is alsoa very complex system that cannot be easily adapted to existingcontinuous flow activated sludge systems.

U.S. Pat. No. 7,459,076 relates to a flow-through aerobic granulatorreactor, which is intended to process continuous wastewater flow, selectand sustain aerobic granular biomass, and accomplish biological nitrogenand phosphorus removal. The reactor may consist of three or four zones.The three-zone system has an anaerobic zone in which influent wastewaterflows through a settled granular sludge bed, an aerobic or operationallyan aerobic/anoxic zone, and a settling zone. The four-zone system has ananaerobic zone in which influent wastewater flows through a settledgranular sludge bed, an anoxic zone that receives recirculated biomassfrom the aerobic zone and effluent from the anaerobic zone, and asettling zone. Airlift pumps periodically transfer solids from theanaerobic zone to the aerobic or anoxic zones. The settling zone, whichhas a series of settling plates, receives effluent flow at a high upwardvelocity (4 meters/hour or greater) to wash out lighter flocculentbiomass with settling of the separated granules directed to theanaerobic zone.

U.S. Pat. No. 7,459,076 selects for only granular sludge and washes outflocculent sludge entirely. It provides influent feeding only throughsettled sludge. It may also be energy inefficient due to the need todepend on sufficient aeration air lift to accomplish recirculation offlow from the aerobic to anoxic zone. It also requires multiple air liftpumps to move granules from the anaerobic to the aerobic zone. Itsphysical arrangement of the zones would not be adaptable to manyexisting activated sludge systems.

U.S. Pat. No. 9,242,882 relates to a method used to waste excess sludgeand select for heavier settling solids in an activated sludge process toimprove the activated sludge settling characteristics as measured by theSludge Volume Index (SVI). This is accomplished by passing the wastesludge stream through some type of gravimetric separator with thelighter solids wasted from the biological treatment system and theheavier solids returned to the biological process. The patent indicatesthat the gravimetric separator could be any process that selects andretains solids with superior settling properties. The patent describesthe separator as receiving the process stream from the biologicalreactor, returning a stream from the separator with the solids withsuperior settling properties to the biological process, and wasting theremaining solids stream from the separator for sludge processing. Analternative approach described is feeding a stream from the bottom ofthe secondary effluent clarifier to the separator and feeding theseparated heavier solids to the biological process and wasting thestream with the lighter solids. The process description states that thegravimetric separator devices include a settling tank, a settlingcolumn, cyclone, hydrocyclone, and centrifuge as examples of apparatusin this application.

U.S. Pat. No. 9,242,882 is not used in the treatment system process andonly relates to handling the smaller waste activated sludge stream withwasting of lighter solids from the waste sludge. It does not address theability to provide process conditions that favor the growth of granularbiomass over flocculent biomass. Lack of or poor growth conditions forgranular sludge will limit the ability to sustain granular sludge andthe reactor mixed liquor solids concentration attainable.

U.S. Pat. No. 9,758,405 relates to a parallel operation of aconventional flocculent activated sludge process and a SBR granularactivated sludge process with influent flow split to the two processes.The flocculent activated sludge process handles hydraulic variations ininfluent flow, while the parallel granular sludge SBR is operated withcontrolled batch feed in the same way as described in U.S. Pat. No.7,273,553 for production of PAO-containing granules. In this way thepractical problem of variations in influent flow rates are handled bythe existing flocculent activated sludge process by having continuousflow gravity separation final clarifiers for separation of treatedeffluent and return of thickened activated sludge to the process. Theparallel granular sludge SBR system provides additional wastewatertreatment capacity and is also intended to increase the biomassconcentration and capacity of the parallel flocculent activated sludgesystem by wasting excess granular sludge produced to the flocculentactivated sludge system. The average particle size of the granularsludge wasted to the flocculent activated sludge system is stated in thepatent to be less than the average size of the granules in the SBRsystem but greater than the activated sludge floc in the flocculentactivated sludge system.

U.S. Pat. No. 9,758,405 does not provide a means for assuring the growthand retention of the PAO granular sludge added from the sidestream batchreactor to the parallel activated sludge reactor. There is notnecessarily an influent wastewater/activated sludge contact zone forgrowth of PAO granules or other type of zones to favor substrate uptakeby granules over flocculent biomass. In addition, the solids retentiontime of the granules added to the continuous flow flocculent activatedsludge process would be the same as for the flocculent sludge. Thus, itonly provides a marginal benefit in the performance of the parallelactivated sludge process.

SUMMARY OF THE INVENTION

A method is provided for a continuous flow combined granular andflocculent activated sludge wastewater treatment process to removeorganics, particulates, nitrogen, and phosphorus to low effluentconcentrations with a smaller footprint than the traditional flocculentactivated sludge process. The process selects for granule biomasscapable of phosphorus and nitrogen removal and controls the average sizeof the granular sludge and the granular and flocculent sludgeconcentrations and solids retention times (SRTs).

The method comprises feeding influent wastewater to the first reactor ofan anaerobic process zone at a soluble BOD volumetric loading rate ofequal to or greater than 0.20 g soluble bCOD per liter per day, whichalso receives recycle of granular sludge from a granular sludgeclassifier, sometimes called separator herein, with the continuous flowtreatment system. The anaerobic process is followed by an aerobicprocess and then mixed liquor flow from the aerobic process flowsthrough a granular sludge classifier at a desired hydraulic loading tocontrol the granule separation from the flocculent sludge at the desiredgranular size. Flocculent sludge and smaller granules are contained inthe flow from the classifier to the secondary clarifier. The flocculentsludge and other particulates settled to the bottom of the secondaryclarifier and the clarifier effluent flow has a low TSS concentration,which enables the system to meet effluent treatment needs. Flow from thebottom of the classifier containing mainly granular sludge is recycledto the first mixed reactor of the anaerobic process zone. The underflowof the secondary clarifier which contains mostly flocculent sludge and amuch lesser amount of granular sludge is recycled to the aerobic processzone. Some portion of the secondary clarifier underflow is wasted fromthe system to control the solids retention time (SRT) and concentrationof flocculent sludge in the aerobic process zone. Some portion of theclassifier underflow can also be removed to wasting for control of thesystem granular sludge concentration and SRT. The first reactor in theanaerobic process zone may be followed by one or more additionalanaerobic reactors in series. The aerobic process may consist of one ormore aerated mixed reactors in series. DO control is used to set a DOtarget concentration in at least the first aerobic zone reactor forsimultaneous nitrification and denitrification and phosphorus uptake bythe granule biomass. The DO concentration setting allows the outsidelayers of granules to be aerobic with nitrification and a large enoughanoxic inner granule volume to allow for denitrification by the PAOs.Control of the flow rate and liquid velocity in the classifier within adesired range for granule size selection is enabled by a bypass flowfrom the aerobic process zone around the classifier to the secondaryclarifier in the case of high influent flow. In the case of low influentflow the flow rate to the classifier remains at the desired level byrecycle flow of the classifier effluent to the classifier inlet and/orby recycle flow from the secondary clarifier underflow return sludgeline.

The method may be a modification of the method described above by havingan anoxic process zone between the anaerobic process zones and theaerobic process zone. The first reactor in the anoxic process zonereceives flow from the last reactor in the anaerobic process zone andmixed liquor recycle flow from the aerobic process zone, which containsNO₃/NO₂. The anoxic process zone may consist of one or more mixedreactors in series.

The method may consist of an anoxic and aerobic process configuration toprovide nitrogen removal without EBPR. This method involves feedinginfluent wastewater at a volumetric loading rate equal to or greaterthan 0.20 g soluble biodegradable COD per liter per day to a first mixedreactor in an anoxic process zone, with the anoxic process zone followedby an aerobic process and then mixed liquor flow from the aerobicprocess through a granular sludge classifier at an desired upflowvelocity to control the desired granular size. The classifier effluentflows to a gravity secondary clarifier for effluent clarification andsettled solids removal. Flow from the bottom of the classifiercontaining mainly granular sludge is recycled to the first reactor ofthe anoxic process some. The underflow of the secondary clarifier whichcontains mostly flocculent sludge and a much lesser amount of granularsludge is recycled to the aerobic process zone. Some portion of thesecondary clarifier underflow is wasted from the system to control theflocculent sludge concentration in the aerobic process zone. Someportion of the classifier underflow can also be removed to wasting tocontrol the granular biomass concentration and SRT in the anaerobic andaerobic process zones. The first reactor in the anoxic process zone maybe followed by one or more additional anoxic reactors in series. Theaerobic process may consist of one or more aerated mixed reactors withDO control in at least the first reactor to allow for simultaneousnitrification and denitrification. The flow rate to the classifier isalso controlled in the same way as above to enable the selection ofgranular sludge within a desired size range.

The methods may comprise having two or more anaerobic reactors in seriesin the anaerobic process zone that are operated with the ability to turnoff mixers over long time intervals to allow granules and solids tosettle into a bottom sludge layer for fermentation to generate VFAs athigh concentration for consumption by PAOs. The mixers would be turnedon for a few minutes after off periods of 12 hours or more of to releasethe solids for movement to the next tank. This anaerobic reactor mayalso receive a portion of the secondary clarifier recycle sludge flow toprovide additional organic material for fermentation. The localized highVFA concentration around the settled granular sludge provides a higherbulk liquid soluble bCOD concentration to drive substrate at sufficientdepth to generate larger granular size.

The methods may include adding an exogenous source of soluble bCOD tosupport sufficient PAO growth or denitrification rates. For system lowin feed soluble bCOD external sources of VFA or other bCOD may be addedor process operation can be modified to produce VFAs. Common sourceswould be from a side reactor fermentation of waste primary sludge orpurchase of industrial carbon such as glycerol, ethanol and acetate.

The methods may include having two or more anoxic reactors in serieswith a high soluble bCOD load to the first anoxic reactor receiving theclassifier granule recycle stream and the influent wastewater.

The methods may include upflow or downflow granular sludge classifierdesigns that are located between the bioprocess and secondary clarifier.

The methods may include upflow or downflow granular sludge classifierdesigns that are located in the final tank of the bioprocess.

The methods may include upflow or downflow granular sludge classifierdesigns that are located in the secondary clarifier.

The methods may include a radial flow energy dissipator and flowdistributor apparatus located in a granular sludge classifier.

The methods may include a downflow energy dissipator and flowdistributor apparatus locate in a granular sludge classifier.

The methods may include designs for the energy dissipator that disruptthe granule/floc sludge matrix to free granules and floc.

The granular sludge must be of sufficient size to meet a high SNDefficiency so that the outer aerobic fraction of the granule is not alarge fraction of the granule biomass and the inner anoxic zone is largeenough for the necessary anoxic PAO population and bioreactions. Thesize of the granular sludge also affects the sludge settling andthickening properties. As the granular size becomes larger the granularsludge settles faster and thickens better and is more capable of SND.However, if the size is too large the biomass is used less efficientlyfor ammonia and nitrogen removal. Larger granules have less surface areaper mass and thus less area for growth of nitrifying bacteria growth. Iftoo large there is a lower nitrification and nitrogen removalefficiency. A proper size range provides both good granule sludgeseparation and selection and good nitrification and nitrogen removalefficiency.

Results reported for a SBR pilot plant provided information on factorsthat affect the granular size and SND efficiency. The reactor was 8 fthigh, 1 ft diameter and treated a stream rich in NH₃—N with acetateaddition for PAO growth. It was operated with a 1-hour anaerobic contacttime with acetate addition, 4.5 hour aerobic condition at a DO of about2.0 mg/L and short settling and decant times. Change in settling timeprovided information on the needed settling velocity of the granules toremain in the system and the size of granules obtained for thesesettling velocities. As shown in FIG. 2, granule sizes above 0.80 mmwere sufficient to have a settling velocity of 11.2 m/h. This is muchhigher than the typical settling velocity of 0.5-1.0 m/h for flocculentsludge.

As the acetate feed loading was increased the average granule sizeincreased and the SND efficiency increased to 85-99% for nitrogenremoval. At a soluble bCOD loading above 0.3-0.4 g/L-h, the granule sizeincreased to a range of 0.95 to 1.1 mm. At higher soluble bCOD loadingsthe bulk liquid soluble bCOD concentration is higher and soluble bCODdiffuses deeper into the granular depth for PAO assimilation and growthto thus produce larger size granules. Thus, a high loading is needed tofavor granule growth at 1.0 mm size and greater.

Results showed that the 1.0-1.2 mm size range provided sufficientsurface area for nitrification at a reactor loading of >0.40 g NH₃—N/L-dand high granular sludge settling velocity. The effect of the organicloading and settling velocity for granule selection is an importantfeature of the activated sludge process configuration and classifieroperation.

A prototype pilot upflow hydraulic classifier was tested for theseparation of a granular/floc sludge mixture. The activated sludge andgranules were grown on two different wastewater sources and reactors ata municipal wastewater treatment plant. The amount of granules availableallowed a test feed concentration of 1300 mg/L as granular sludge andgranule 800 mg/L for the flocculent sludge. The SVI₃₀ of the granule andflocculent sludge were 35 and 210 mL/g, respectively. The averagegranule size was 1.1 mm.

The classifier (separator) operating conditions provided an upflowvelocity of 10.8 m/h. The classifier underflow contained 94% of thegranules fed for a 6% rejection to the stream and 36% of floc for a 64%rejection to the stream. Such a stream in the continuous flow processdescribed in this disclosure would go to a secondary clarifier.

A mass balance analyses was done to determine the relativeconcentrations and SRTs of granules and flocculent sludge in thebioprocess as a function of the granular sludge classifier performanceand all solids wasting from the secondary clarifier underflow. The massbalance is based on three key fundamentals found in the wastewaterengineering textbook by Tchobanoglous et al. (2014): 1) the solidsconcentration in a bioprocess is equal to the solids production ratetimes the solids SRT divided by the bioprocess volume, 2) at steadystate operation the solids production rate is equal to the solidswasting rate, and 3) the SRT of the solids is equal to the solids massin the bioprocess divided by the amount of solids wasted per day. Thismass balance was done separately for granular and flocculent sludge. Therelative amounts of each wasted is proportional to their relativeconcentrations leaving the granular sludge classifier. For example, ifthe effluent from the classifier contains 90% of the flocculent sludgeand 10% of the granular sludge fed to the classifier, then thebioprocess will have the reverse concentrations of 90% granular sludgeand 10% flocculent sludge. Results of this mass balance are shown inFIG. 3, which shows a graph of the granular to floc SRT ratio as afunction of the classifier reject percentages.

The graph results in FIG. 3. are used to assess the efficiency of theclassifier (separator) test result and show very acceptable and goodperformance the upflow classifier design and operation. At a 10%granular sludge reject and 65% reject for flocculent sludge, the systemSRT for the granules is 6.5 times that of the flocculent sludge. Thus,if the flocculent sludge MLSS concentration is 1,200 mg/L for goodclarification the granular sludge MLSS concentration could be as high as7,800 mg/L. The combined flocculent/granular sludge concentration couldthen be 9,000 mg/L, which is about 3 times higher than used forconventional activated sludge processes for biological nutrient removal.Higher reject efficiencies lead to higher granular mixed liquor to flocmixed liquor concentrations.

In one particular embodiment of the invention a sidestream takes aportion of sludge from an aerobic zone of the system, the sidestreamincluding a classifier or separator for producing an effluent with anincreased concentration of granular biomass. Another effluent of thisseparator is rich in floc, and much of this is wasted. The granule-richsludge goes to a clarifier, which may include a second separator withinthe clarifier, for further concentration of granules.

The anaerobic process zone preferably has multiple stages and isconfigured and operated to encourage solution growth of granular biomassin subsequent process zones.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows stereo microscope photos comparing flocculent andself-aggregating aerobic granular sludge size and structure.

FIG. 2 is a graph showing relationship of granular size, settlingvelocity and bCOD loading rate.

FIG. 3 is a graph showing relationship of a system granular to floc SRTratio as function of floc and granular sludge reject efficiency from ahydraulic separator of the feed.

FIG. 4 shows schematic of general arrangement of continuous flowcombined granular/floc sludge process.

FIG. 5A shows schematic of a variation of the process for a phosphorusand nitrogen removal including simultaneousnitrification-denitrification.

FIG. 5B shows schematic of a variation of the process for a phosphorusand nitrogen removal including simultaneousnitrification-denitrification for treating wastewater with a lowersoluble bCOD fraction.

FIG. 5C shows schematic of a variation of the process for nitrogenremoval with anaerobic granule selector zone.

FIG. 5D shows schematic of a process for production of granular sludgein sidestream treatment for feeding granules to the main wastewatertreatment process.

FIG. 6A shows schematic of a downflow granular sludge classifier.

FIG. 6B shows schematic of a upflow granular sludge classifier.

FIG. 7 shows schematic for locating the granular sludge classifier inthe bioprocess.

FIG. 8A shows schematic of a downflow granular sludge classifier locatedin the secondary clarifier.

FIG. 8B shows schematic of a submerged upflow granular sludge classifierlocated in the secondary clarifier.

FIG. 9 shows schematic of a variation of the process for nitrogenremoval with anoxic granule selector zone.

FIGS. 10A-10D show schematics of a radial flow energy dissipating inletwith radial flow for use in a granular sludge classifier or separator.

FIGS. 11A-11B show schematics of an energy dissipating inlet for agranular sludge classifier or separator utilizing a downflow separationdesign.

FIG. 12 is a schematic diagram showing a particular embodiment with asidestream separator, which may be in addition to a separator in theclarifier.

FIG. 13 is an elevational section view showing a multiple-stageanaerobic zone for the system of the invention, to encourage selectivegrowth of granular sludge.

DESCRIPTION OF PREFERRED EMBODIMENTS

All of the combined granular/flocculent sludge processes shown are forcontinuous flow activated sludge treatment using hydraulic granularsludge classifier or separator to control granule size and to providegranule recycle to a first high loaded anaerobic or anoxic reactor. Bycontinuous is meant essentially continuous, possibly including startsand stops but not batch process. The classifier provides a means tocontrol the size of the granular sludge and the flocculent and granularsludge concentrations in the treatment reactor activated sludge mixedliquor. A minimum flocculent sludge concentration is needed forefficient degradation of colloidal and suspended solids in thewastewater and to provide good effluent clarity.

The flocculent sludge concentration may vary as a function of thewastewater characteristics and will be typically in the range of500-1,500 mg/L. A preferred range of flocculent sludge for solidsclarification for capture of particulates and colloidal solids is 800mg/L-1,200 mg/L. The granular size is controlled to provide a low SVIand a high MLSS concentration and for maintaining high efficiencysimultaneous nitrification-denitrification (SND) and enhanced biologicalphosphorus removal (EBPR). The size must be large enough to provide asufficient anoxic volume in the granules in the aerobic reactor for SNDand PAO growth, but small enough to provide efficient use of biomassgrowth for EBPR and have enough surface area for efficientnitrification. The granules may have a size range from 0.3 mm-3.0 mm.The preferred size may be in the range of 0.7 mm-2.0 mm. The effluentfrom the classifier has a much higher concentration of flocculent sludgethan granular sludge and these solids are settled in the secondaryclarifier. The secondary clarifier can be circular, rectangular orsquare. Wasting of sludge from the bottom flow from the secondaryclarifier results wasting more flocculent than granular sludge from thesystem to thus result in a much higher granule sludge concentration inthe bioprocess. Concentrations and SRTs in the reactor mixed liquor. Thegranular sludge concentration in the mixed liquor may be 2-8 times theflocculent sludge concentration, or in the first process zone, typically2-3 times. Due to the high settling rates and high thickness of thegranular sludge the bioprocess may have a reactor mixed liquorconcentration 2-3 times that of conventional flocculent activated sludgesystems and up to a typical operating range of 6,000 mg/l-12,000 mg/L tosave on treatment footprint and tank volume required. The hydraulicseparator provides an upflow velocity that carries out mostly flocculentsolids to be removed by the final clarification step.

Granule settling velocity changes with granule size and thus thehydraulics of the classifier are controlled to select for the desirablegranular size. Other types of classifiers may be used in thecombined/flocculent sludge processes for granule size selection and flocseparation such as screens or hydrocyclones.

FIG. 4 shows a general arrangement of the process for granule selectionand granule size and concentration control. Granular sludge recycle flowline 21 enters an anaerobic or anoxic reactor 36 at high soluble bCODloading where it is mixed with the influent wastewater line 16. Flowfrom the high loaded reactor is further processed in a downstreamaerobic or anoxic reactors and in aerobic reactors consisting of one ormore baffled stages. The flow from the final aerobic process line 28enters the classifier 10 which has a separation means that produces twooutflow streams. One flow contains mostly flocculent sludge line 22which is directed to the secondary clarifier. The other flow containsmostly granules which is directed to the first reactor via line 21 withpossible removal of a small portion via a line 26 for granular sludgewasting.

Flow control methods are used to maintain the hydraulic loading on theclassifier with possible upflow velocities in the range of 5-20 m/h(meters per hour) to control granule size selection and maximize theflocculent sludge rejection efficiency. Rejection represents thefraction of granule or floc solids from the influent line 28 that is inthe classifier effluent line 22. A high rejection percentage occurs forthe smaller size flocculent sludge and a lower rejection percentageoccurs for the larger size faster settling granules. A portion of theflow leaving bioprocess may be bypassed around the classifier in abypass line 30 to divert higher flows during diurnal flow variations ordue to wet weather events to control the flow rate to the classifier.When the influent wastewater flow results in lower than a desired rangeof flow to the classifier, recycle may be provided from the classifiereffluent line 32 and/or by increasing the flow of clarifier returnsludge line 18. Short cut recycle from line 18 can be used to directrecycle sludge flow to the classifier via line 19.

Sludge wasting must be done to control the activated sludge MLSSconcentration at its desired levels. The primary location for wastingexcess solids is line 34 from the secondary clarifier. The classifierprovides a higher percentage of flocculent sludge to the clarifier dueto the higher reject efficiency for the smaller solids. Thus, thesecondary clarifier underflow has a higher fraction of flocculent sludgeand wasting from that line results in a bioprocess with a much highergranular sludge concentration than flocculent sludge.

The sludge management approach is also to select the solids wasting ratefrom the secondary clarifier underflow line 34 to meet the flocculentsludge concentration needed to provide good clarification and low TSS inthe effluent. If the SRT and bioprocess concentration of the granularsludge is too high than additional granular sludge can be wasted fromthe classifier underflow line 26.

The embodiments illustrated in FIGS. 5A, 5B, 5C, FIG. 5D, and FIG. 9 arefor continuous flow combined granular/flocculent activated processeswith different process features to meet the specific treatmentobjectives, handle different types of wastewater characteristics andselect for the preferred type of granular sludge. They all incorporate ahigh loaded first reactor and granular sludge classifier to control thegranular sludge size and relative proportions of granular and flocculentsludge in the activated sludge mixed liquor. Granule size control isimportant for providing an aerobic reactor with SND, which reducesenergy costs for aeration and internal recycle pumping and a simplertreatment scheme than conventional nitrification and denitrificationprocesses for nitrogen removal.

The first embodiment shown in FIG. 5A is a continuous flow combinedgranule/flocculent sludge process to grow granules with PAOs and toallow SND to achieve for both biological nitrogen and phosphorusremoval. The process has an anaerobic zone 38, an aerobic zone with SND40, a final aerobic zone at higher DO 52, granular sludge classifier 10,and a secondary clarifier 14.

Granular sludge is recycled from the classifier line 21 to an anaerobicreactor 42 with a volume that result in a high soluble bCOD loading fromthe influent flow line 16. The anaerobic zone may have at least 3 stages(3 mixed reactors in series) with the first reactor at a high solublebCOD loading of greater than 4.8 g soluble bCOD/L-day and less than 30 gsoluble bCOD/L-day. The 2^(nd) stage volume 44 is at least as large asthe 1^(st) stage and preferably no more than double. The 3^(rd) stage 46is much larger and can exist as a single tank or be divided intomultiple stages. The high soluble bCOD loading assures a higher bulkliquid soluble bCOD concentration and creates a long enough diffusiongradient to drive substrate deeper into the granules for subsequentoxidation by NO₃/NO₂ for SND in the aerobic zone to enable larger sizegranules.

Mixed liquor from the anaerobic zone enters 38 enters an aerobic reactor40 that has DO control to allow SND. If DO concentration is too highthen oxygen penetrates too deep into the granule to limit use of NO₃/NO₂by the PAOs. If too low the nitrification rate on the outer layer of thegranules is too low to result in a low nitrification efficiency. A lowernitrification efficiency can lead to less nitrogen removal.

The aeration tank 40 can be a single aerated mixed tank or divided intoa number of tanks in series. Aeration DO control maintains the DOconcentration at set points in the range of 0.5 mg/L-2.5 mg/L dependingon the MLSS and granular size so that SND occurs for nitrogen removal.Nitrifying bacteria growth is primarily on the outer layers of thegranule, where the DO concentration is higher, and PAOs are generally inthe inner core of the granule, which can use NO₃/NO₂ produced bynitrifying bacteria in the outer granule.

The classifier (separator) and secondary clarifier process and operationis the same as that described for FIG. 4 above. One exception is thatthe increased return activated sludge recycle flow to control theclassifier velocity may also be provided in a separate flow line 19 fromthe return flocculent sludge recycle instead of only increasing the flowin line 18.

The sludge wasting to control the bioprocess granular and flocculentsludge concentrations is the same as described for the generalconfiguration in FIG. 4 above.

Anaerobic zone stages after the first stage 42 may be operated withon/off mixing to allowed solids settling and fermentation of solids toproduce more localized soluble bCOD for uptake by granules with PAOs.Some return activated sludge flow line 18 a may be added to theanaerobic stage with on-off mixing to provide other solids that can befermented to produce soluble bCOD.

A modification to Embodiment 1 for wastewater with a low influentsoluble bCOD relative to the influent total organic and ammonia nitrogenis shown in FIG. 5B. The modification relies on the degradation ofparticulate and colloidal solids to provide degradable COD fordenitrification. This process contains an anaerobic zone 38 anoxic zone50, a SND aerobic zone 40, a second aerobic zone 52, a low DO zone 54, agranular sludge classifier 10, and a secondary clarifier 14.

This process is necessary for applications lacking enough soluble bCODto enable high removal of nitrogen by SND with PAO granular sludge. Dueto the low soluble bCOD:N ratio the amount of stored carbon by PAOs inthe anaerobic zone cannot provide enough electron donor to consume ahigh percentage of the amount of NO₃/NO₂ produced in the aerobic zone.An internal recycle flow, line 56, from the low DO zone 54 within thesecond aerobic zone 52 provides NO₃/NO₂ to the unaerated mixed anoxiczone 50 for consumption of NO₃/NO₂ with oxidation of particulate andcolloidal solids. The internal recycle flowrate may range from 50 to500% of the wastewater influent flowrate. The anoxic and aeration zonesmay consist of a single reactor or a number of reactors operated inseries.

Additional carbon is provided by biodegradable colloidal and suspendedsolids in the preanoxic zone 50 before the aerobic SND zone 40. Theadditional aerobic zone 52 operated at a higher DO concentration isprovided after the SND aerobic zone for further NH₃ oxidation andenhance further P uptake.

For this process all the features and operational conditions of theanaerobic zone 38, SND aerobic zone 40, final aerobic zone 52 describedfor FIG. 5A are applicable. Also, all the features and operationalconditions described for the classifier and clarifier and sludgemanagement are applicable and clarifier operation described inEmbodiment 1 above with FIG. 5A are included.

A modification to Embodiment 1 for applications for which nitrogenremoval and not phosphorus is required is shown in FIG. 5C. An anaerobichigh loaded first reactor is used to select for PAO granules. Mixedliquor flows from anaerobic reactor 44 to an anoxic zone 50 that may besingle or multiple stages. The PAO granules from reactor 44 use storedcarbon obtain in reactors 42 and 44 for denitrification in zone 50. FIG.5C also shows a clarified effluent recycle line 57 for dilution of theinfluent to the classifier/separator 10, to achieve optimum dilution forseparation of granules, as needed. This is an option for all of FIGS. 4to 5C, and even for FIG. 5D, discussed below, in which clarifiedeffluent from the main process can be cycled to the separator fordilution. Other sources of clarified liquid or water could also be usedfor this purpose. See dilution line 57 in FIG. 5D.

Embodiment 2 shown in FIG. 5D is used for growth of granules to add tothe main treatment system and does not itself have a final secondaryclarifier as in Embodiment 1. The system is a sidestream incubator forgranular sludge. The first high loaded anaerobic reactor 42 a is fedline 16 a which may be, for example, a reject liquid from digestiondewatering or a small portion of the influent wastewater flow, oranother wastewater stream, MLSS from one of the main process zones, oreven industrial wastewater, with addition of other organics ifnecessary. The process selects for PAO granules that are fed via line 26a to a liquid treatment system producing the treated effluent for thewastewater treatment plant, e.g. to the main process systems of FIGS. 4and 5A to 5C, preferably to an anaerobic zone as at the line 21 in FIGS.4 to 5C. Effluent from the anaerobic zone is preferably fed to ashort-SRT aerobic zone 52 a but could also be fed first to an SNDaerobic zone 40 a followed by a longer-SRT aerobic zone 52 a. Theclassifier overflow final effluent line 23 a is also fed to the mainliquid treatment system, preferably to an aerobic or anoxic zone.Treatment of influent flow 16 a follows the same course as for thesystem in FIG. 5A to produce PAO granules. Recycle of underflow from theclassifier or separator 10 d in FIG. 5D is directed to reactor 42 aoperated at a high soluble bCOD load.

The sludge classifier (separator) is the key component for the controland optimization of granular/flocculent activated sludge processes.

The sludge classifier or separator uses a hydraulic design to controlthe relative capture efficiency of granules and floc and to also controlthe size of the granular sludge. The classifier is a downflow or upwardfeed and upflow effluent design that separates the appropriate solidssize as a function of the apparatus upflow velocity. The upflow velocityis greater than 1.0 m/hr to minimize floc settling in the lower chamber.The classifier/separator may be contained in the bioreactor tankage asshown in FIG. 7, located between the bioreactor and liquid/solidsseparation clarifier as shown in FIGS. 6A and 6B, or located within aconventional secondary clarifier as shown in FIGS. 8A and 8B.

A schematic of the granular/flocculent downflow classifier 10 a locatedbetween the bioreactor and liquid/solids separation clarifier is shownin FIG. 6A. The effluent flow line 28, from the aerobic process zoneplus classifier effluent recycle flow line 32, enters an energydissipater 60, preferably but not necessarily submerged, thatdistributes a uniform down flow of the mixed liquor and promotesseparation of granule and floc. The flow travels downward in the innerchamber 62 and the fast settling granules continue to settle to thebottom of the classifier. A majority of the flow from the inner chamberflows to the outer chamber 63 and the resulting liquid rise velocity inthe outer chamber is greater than the floc settling velocity of floc,which causes floc to be carried upward and out with the flow over theeffluent launder 64 to the secondary clarifier through the classifiereffluent line 22. Due to the fact, granular sludge has a much highersettling velocity than flocculent sludge, the solids rising in the outerchamber will consist mainly of flocculent sludge. The rise rate can alsobe controlled to select for granular size by varying the recycle flowrate line 32. At very high flow rates, due to peak diurnal flow or wetweather flow, a portion of the influent flow to the classifier can bebypassed using the high flow bypass line 30 to the secondary clarifierso that the classifier's preferred rise rate is maintained. The granulesare collected and thickened at the bottom of the classifier 10 a andexits via line 20 to continuous flow recycle line to the high loadgranular biomass selector tank at the beginning of the upstreamactivated sludge process and also split to a waste line to be used asneeded.

A schematic of the granular/flocculent sludge upflow classifier 10 blocated between the bioreactor and liquid/solids separation clarifier isshown in FIG. 6B. The influent feed from the activated sludge bioreactorline 28 plus the effluent recycle flow line 32 is introduced into theenergy dissipater 68 preferably submerged and located at an appropriatedepth within the classifier that distributes a uniform radial flow andpromotes separation of granules and floc. Preferably the dissipater isbetween one-third and two thirds of the classifier tank liquid depth, orwithin 30% of center of the tank's depth. The classifier's dimension andtotal feed flow rate determine the upflow velocity in the upper regionof the chamber 66 to separate granules and floc and determine thegranule size. The granules with settling velocity greater than theupflow velocity are captured and thickened at the bottom of theclassifier 10 b and exits via line 20 to a continuous flow recycle lineto the high load granular biomass selector tank at the beginning of theupstream activated sludge process and also split to a waste line to beused as needed. The rise rate can also be controlled to select forgranular size by varying the recycle flow rate, line 32. At very highflow rates due to peak diurnal flow or wet weather flow a portion of theinfluent flow to the classifier can be bypassed using the peak flowbypass line 30 to the secondary clarifier so that the classifier desiredrise rate is maintained.

In a preferred embodiment of the system of the invention the classifierprocesses at least two times daily system influent volume per day.

The general schematic in FIG. 7 illustrates that the classifier can belocated in the bioprocess, typically after the last aeration reactor.Granular sludge recycle flow from the classifier line 21 enters agranular feed reactor 36 at a high soluble bCOD loading where it ismixed with the influent wastewater line 16. The granular feed reactor 36may be anaerobic (as in FIGS. 5A, 5B, and 5C) or anoxic (as in FIG. 9).The bioprocess zone 48 after the granular feed reactor may contain aseries of anaerobic, anoxic and aerobic reactors in some configuration.Mixed liquor flow from a final bioprocess reactor enters the classifier10 and most or all of the flow in the classifier underflow line is inthe granular sludge recycle line 21 or a lesser amount for granularsludge wasting line 26. Flow control to the classifier at low influentflow conditions may be provided by recycle of flow from the classifiereffluent line 22 back to the classifier inflow via line 32 and/or byincreasing the flocculent sludge recycle flow rate from the secondaryclarifier 14 via line 18. At excessive high flow conditions bioprocesseffluent flow beyond that desired for the classifier may be directedfrom the final bioprocess reactor to the clarifier 14 via line 30. Thetotal influent flow line 23 to the clarifier 14 equals the clarifiereffluent flow following solids settling line 24 plus clarifier underflowwith a thicker flocculent sludge concentration in a recycle flow to thebioprocess 48 and a small amount of flow for mainly flocculent sludgewasting line 34.

A schematic of the granular/flocculent downflow classifier locatedwithin a conventional secondary clarifier is shown in FIG. 8A. Theeffluent flow line 28 from the activated sludge bioreactor plusclarifier floc recycle flow line 19 enters an energy dissipater 70 thatdistributes a uniform down flow of the mixed liquor and promotesseparation of granules and floc. Alternatively, the recycle flow rate tothe bioprocess in line 18 could be increased. The flow travels downwardin the inner, classifier chamber 72, the granules are settling fasterthan the floc. Floc from the classifier chamber 72 flows into the outer,secondary clarifier chamber 74 with an upflow velocity that liftsparticles with settling velocity less than the rise velocity. Flow istoward the effluent launder 76. Floc then is allowed to settle to thebottom of the secondary clarifier chamber 74 and the clarifier liquid iscarried into the effluent launder and out through the clarified effluentline 96. Due to the fact that granular sludge has a much higher settlingvelocity than flocculent sludge, the solids leaving the classifierchamber 72, i.e. flowing outwardly between an upper annular deflector 80and a lower annular sludge dividing deflector 82 will consist mainly offlocculent sludge. The rise rate in the classifier chamber 72 can alsobe controlled to select for granular size by varying the clarifier flocrecycle flowrate line 32. At very high flow rates due to peak diurnalflow or wet weather flow a portion of the influent flow to theclassifier can be bypassed using the high flow bypass line 30 to aseparate secondary clarifier so that the classifier preferred rise rateis maintained. The granules are collected and thickened at the bottom 78of the classifier chamber 72 and recycled, via line 84, to the highloaded first reactor of the upstream activated sludge process. The flocare also collected and thickened at the bottom of the secondaryclarifier chamber 74 and recycled, via line 86, to the appropriatelocation in the upstream activated sludge process.

A schematic of a more preferred embodiment of a granular/flocculentupflow classifier located within a conventional secondary clarifier isshown in FIG. 8B. The effluent flow from the activated sludgebioreactor, line 28, plus clarifier floc recycle flow line 19 enters anenergy dissipater, flow distribution, and granule/floc separation device88 located at an appropriate depth within the inner, classifier chamber92, preferably below center as shown. This combined influent flow entersthe separation device 88 via ports (not shown) in the center influent 90of the clarifier. The flow travels upward and outward, the granules aresettling faster than the floc and tend to settle in the classifierchamber 92 of the clarifier. Floc from the classifier chamber 92 flowsinto the outer, secondary clarifier chamber 94 with an outward andupward flow velocity that lifts particles with settling velocity lessthan the rise velocity. Again, upper and lower annular deflector plates80 and 82, respectively, help direct flow in and out of the classifierchamber 92. Floc flows out of the classifier chamber to the secondaryclarifier chamber 94. Floc is allowed to settle to the secondaryclarifier floor in the secondary clarifier chamber and the clarifiedliquid is carried into the effluent launder 76 and out through theclarified effluent line 96. Due to the fact that granular sludge has amuch higher settling velocity than flocculent sludge, the solids leavingclassifier chamber 92 will consist mainly of flocculent sludge. The riserate in the classifier chamber 92 can also be controlled to select forgranular size by varying the clarifier floc recycle flowrate line 19. Atvery high flow rates, due to peak diurnal flow or wet weather flow, aportion of the influent flow 28 to the classifier can be bypassed usinga high flow bypass line 30 to a separate secondary clarifier so that theclassifier preferred rise rate is maintained. The granules are collectedand thickened at the bottom of the classifier chamber 92 and recycledline 84 to high loaded first reactor of the upstream activated sludgeprocess. The floc are also collected and thickened at the bottom of thesecondary clarifier chamber 94 and recycled, via line 86, to theappropriate location in the upstream activated sludge process.

Embodiment 3 shown in FIG. 9 is for a continuous flow combinedgranular/flocculent sludge process for nitrogen removal where phosphorusremoval is not needed. No anaerobic zone is used in this case and thegranules grown are based on the classifier operation and the solublebCOD loading to the first stage reactor 54 of the anoxic zone 50. Theprocess contains an anoxic zone 50, an aerobic zone 40, a granularsludge classifier 10 and secondary clarifier 14. The second anoxicreactor 58 may be single stage or divided into two or more stages. Theaerobic zone 40 may also be single stage or divided into two or morestages.

All the features and operational conditions described for the classifierand clarifier and sludge management are applicable and clarifieroperation described in Embodiment 1 above with FIG. 5A are included.

FIGS. 10A through 10D show an energy dissipating inlet (EDI) 110 thatcan be used in the preferred classifier shown in FIG. 6B. This issometimes called a reverse energy dissipating inlet or reverse EDI, andcan be used upright as in FIGS. 10A and 10B, or inverted as in FIGS. 10Cand 10D. The EDI has a top plate 112, a top deflector plate 114 at theperiphery of the top plate, a bottom plate 116 and a series of outer andinner baffle plates 118 and 120, offset in position as shown in FIG.10D, which shows a preferred inverted condition of the EDI 110. Thesectional view of FIG. 10D is also inverted, showing inner baffles at120 and the outer baffles 118 in dashed lines, since they are instaggered positions with the inner baffles at baffle. In this positionthe top plate 112 is actually at the bottom. As can be seen from FIGS.10C and 10D, flow is down through the influent pipe 122 to the interiorof the EDI, where the baffles dissipate energy, slow and distribute theflow generally evenly into the volume of liquid, tending to separate thefloc and granular sludge, with an upward and outward flow pattern.

FIGS. 11A and 11B show an energy dissipating inlet (EDI) 121 that can beused in the classifier shown in FIG. 6A and in the classifier area ofthe clarifier in FIG. 8A utilizing the downflow separation design. Thisis sometimes called a faucet energy dissipating inlet, and can be usedwith faucet baffles at bottom of the lower deflector 124 as in FIG. 11A,or at the bottom plate 116 as in FIG. 11B. The EDI 121 has a bottomplate and a series of outer and inner baffles (118 and 120) similar tothe reverse EDI 110 shown in FIGS. 10A through 10D. EDI 121 also hasmore baffled layers 119 than EDI 110 with each baffled layer, from themost inner to the most outer, offset from each other to provideincreased energy dissipation and optimum flow patterns to disrupt thegranule/floc matrix for optimum separation of granules from the flocstructure. In addition, upper faucet baffling system in FIG. 11A or alower faucet baffling system in FIG. 11B is added to equalize flowdistribution of the granules which have separated from the flocstructure such that the granules settle over the entire classifier floorarea. The faucet baffle system has openings which vary in size so thatthe beginning flow is restricted from exiting the closest opening andrequires the flow to continue flowing to the next opening until the flowis equalized. The faucet layer can be placed at the lower exit of theEDI 121 which is referred to the lower faucet baffles 126 as shown inFIG. 11A, or this faucet baffle system can replace a portion of thebottom plate 116 at the upper exit which is referred to the upper faucetbaffles 128 shown in FIG. 11B. The lower faucet baffles 126 in FIG. 11Areceive the settled granules from the upper layer of radial baffles atthe outer edge of the bottom plate 116. The lower faucet baffles 126, inthis configuration, restrict all the granules from exiting at the outeredge of the lower deflector 124 requiring the flow to continue flowingto the next opening until the flow is equalized and the granules settleevenly over the entire classifier floor area. In contrast, the upperfaucet baffles 128 in FIG. 11B allow the granules that have settled ateach radial baffle layer to pass through the faucet opening while thefloc is kept suspended, enters an outer annular part, still high up inthe EDI as shown, and finally exits through an annular array of flocdischarge outlets 131 along an upper deflector 130 which directs thefloc 132 outwardly and downwardly into the clarifier area. After passingthrough the upper faucet baffles 128, the granules 134 then settleevenly over the entire classifier floor area of the tank with the lowerdeflector 124 preventing short circuiting into the clarifier area of thetank.

FIG. 12 is a schematic diagram showing another wastewater treatmentsystem of the invention including a classifier or separator forenhancing granular sludge content. In this case the system, the liquidside of a treatment system as shown, includes an influent flow 150 intoa series of biological treatment zones, in this case shown as ananaerobic zone 152, an anoxic zone 154 and an aerobic treatment zone156. The anoxic zone 154 could be a “swing” zone by having aeration at acontrolled rate to have simultaneous nitrification/denitrification, andthe two zones 154 and 156 could be a single anoxic/oxic “swing” zone.Note that each of the process zones may contain one or more tanks inseries.

The system shown in FIG. 12 includes a sidestream generally identifiedas 158, receiving a flow from the zone 156, i.e. from the aerobic oranoxic/oxic zone. Effluent from the zone 156, indicated at 160, isdivided such that a selected portion of this flow goes into thesidestream, at 162. A sidestream separator or classifier, forgranule/floc separation, is indicated at 164, and the sidestream flow isdirected into the separator via a flow line 166. A pump 168 may beprovided for this purpose, although in some cases the flow to theseparator 164 could be by gravity. The influent to the separator 164 isvia an EDI 169, which can be configured as in some of the previouslydescribed embodiments, such that granular sludge is encouraged into abottom region 170 of the separator vessel 172, while primarily flocsludge is collected at an upper end, indicated as overflowing into afloc collection launder at 174.

The drawing also shows an internal recycle flow at 176, from theprimarily floc collection launder 174, dropping by gravity. This recycleflow 176 joins with the incoming sidestream feed flow 162 at acollection box 178. The pump 168 preferably is adjustable, and is set tomaintain a prescribed flow rate, with recycle 176 and incoming feed flow162, through the separator 164 for desired flow velocities in theseparator to encourage separation of granular sludge from floc sludge.In conditions where sidestream flow 162 is minimal, volumetric flow intothe separator should be kept substantially constant, thus the internalrecycle flow loop 176. If conditions are such that the liquid level inthe collection box 178 becomes too low as determined by a sensor, thepump can be automatically shut off.

As indicated in the drawing, a first effluent of the sidestreamseparator, indicated as “SS effluent” in the drawing, at 182, isenhanced in granular concentration and preferably is rejoined with themain flow 160, to be introduced as a combined flow 183 into a clarifier184. A second effluent of the separator 164 preferably comes from theupper end of the separator, in the same manner as the recycle flow 176,and comprises primarily floc sludge. This is indicated as a wastedstream 186 in the drawing, “F-WAS”.

In one implementation of the invention, the combined flow 183 ofgranular-rich sludge and effluent sludge from the process zone 156 canbe delivered into the illustrated clarifier 184 in a conventionalmanner, typically through an energy dissipating inlet (EDI). The sludgeto be settled in the clarifier will be enhanced in granular content, andsince granular sludge settles at a faster rate than floc, the centralbottom 188 of the clarifier will tend to concentrate the granularsludge. However, in the illustrated embodiment the clarifier's EDI 190is a special separator EDI, i.e. a further separator that works inconjunction with the geometry of the clarifier to concentrate granularsludge even further. For example, the EDI can be similar to theseparators shown in FIGS. 11A and 11B, or the clarifier/separatorcombination can be essentially as shown in FIGS. 8A and 8B. In anyevent, the EDI/separator 190 tends to separate granular from flocsludge, depositing granular sludge downward essentially centrally in theclarifier, while floc sludge tends to drift outwardly and to becollected as primarily granular sludge in an outer annular region 192 ofthe clarifier. The clarifier can include a dividing ring 194 to mostlyseparate primarily floc sludge into the outer region 192, whileprimarily granular sludge drops to central bottom region 188.

In FIG. 12 a dashed line 196 is shown for withdrawal of MLSS from adesired level directly from the aerobic process zone 156.

FIG. 12 shows a recycle line 198 (F-RAS) from the primarilyfloc-settling region 192 of the clarifier to the process zone 156, whichmay be an aerobic zone. Also, from this line 198 is shown an effluentline 200 (F-WAS) for wasting a portion of the recycle sludge from theclarifier.

The drawing shows a secondary effluent dashed line 201 which may beincluded from the clarifier's outflow launder back to the sidestream,entering the recycle flow at 176. This is to dilute the sidestreamseparator feed to provide better separation characteristics. Note thatsuch a dilution line can also be included in the systems describedabove, such as in FIGS. 4, 5A-5D and 9, to dilute the flow to theseparator when needed for optimal granular separation. In all cases, thedilution water could come from another source of clarified water ifdesired.

It is also possible that the internal recycle of the sidestream could beeliminated in some treatment plants or daily flow conditions. Thedilution stream 201 from the clarifier, and/or an increase in the rateof flow from the aerobic zone 156, can be used to increase flow throughthe sidestream separator 164 as needed to maintain a minimum flowtherethrough.

Still further, a dashed line 202 is indicated from the SS effluent line182, i.e. granular-enriched sludge from the sidestream separator 164.Since the sidestream includes a granular/floc separator, the primarilygranular portion can be sent directly back to the anaerobic zone 152,without first going to the clarifier 184. If desired the flow could bedivided, according to conditions, to direct a portion of the SS effluent182 to the clarifier and another portion via the line 202 directly tothe anaerobic zone 152 via G-RAS line 203.

Another optional recycle line is shown at 204, indicating that primarilyfloc recycle sludge in the F-RAS line 198 can be recycled to the anoxiczone (or anoxic/oxic zone) 154, rather than (or in addition to)recycling to the aerobic zone 156. Another dashed line 206 shows apreferred recycle of a portion of the sludge in the aerobic zone back tothe anoxic or swing zone 154.

The granular separation system described achieves several advantages.First, it provides two stages of granule/floc separation, so that abetter concentration of granular sludge can help all sludge settle morequickly in the clarifier and a higher concentration of granular sludgecan be realized at the bottom of the clarifier, at 188. Second, byhaving a sidestream separator 164, the system provides an earlyopportunity to collect very light floc and to discharge a desiredportion of that floc, as at 186, rather than allowing the lightweight,fluffy material to hinder settling of sludge in the clarifier. Third,the sidestream allows for adjustment of conditions of the incoming mixedliquor for initial startup of the granular/floc separator, which canrequire dilution to achieve optimum conditions for separation. Fourth,the sidestream provides for the possibility of operation for differentconditions and solids retention times for the AGS and floc. The portionof the effluent flow from the aerobic zone 156 to be sent through thesidestream can be adjusted. To avoid significant variations in flowthrough the separator 164, the pump 168 maintains essentially consistentflow, increasing the internal sidestream recycle to balance lower flowfrom the line 160 to assure a prescribed range of flow through theseparator.

Another aspect of the invention focuses on the anaerobic process zone152, i.e. the zone which first receives the influent flow 150. See FIG.13. Pursuant to the invention the anaerobic zone is a multi-stage zoneconfigured to provide an environment to encourage the growth ofgranules, in further zones downstream. The multi-stage anaerobic zone152 is designed to create intimate contact of the food-bearing incomingwastewater with the recycled activated sludge entering the anaerobiczone (G-RAS as in FIG. 12), with its granular sludge, and with granularbiomass already present in the first anaerobic zone. The influent 150 isrich in readily biodegradable soluble food for the microbes, while theRAS is rich in microbes, as well as in granular biomass. The anaerobictank and its inflows are configured to encourage further granule growthof sufficient size to provide good separation of granules in theseparators downstream. The design encourages a high soluble volumetricBOD loading and also a high food-to-mass (F/M) ratio (mass of BODapplied/mass of MLVSS-day, i.e. mixed liquor volatile suspendedsolids-day), particularly at the influent end of the zone.

One preferred implementation is shown in FIG. 13. In this embodiment,the anaerobic tank 152 is divided into multiple stages, at least two,with FIG. 13 showing three. Incoming wastewater, which may be rawwastewater, is indicated at the left side of the drawing, at 150, andthis is combined with a portion of the G-RAS recycle flow 203 (see FIG.12). The influent wastewater (line 150) and RAS recycle (line 212) arethoroughly mixed for intimate contact before entry to the stage 215,which would occur in a pipe or a mixing box upstream of or within theanaerobic zone. The RAS portion indicated as 212 in the drawing is apreselected portion of the total RAS flow 203 as further discussedbelow. Note that the G-RAS in the recycle line 203 could have beentreated in a nitrate removal tank (not shown) prior to reaching theanaerobic zone 152.

The influent wastewater and the RAS portion flow into the first stage215 of the anaerobic zone, which is a small AGS feed stage withretention time preferably 30 minutes or less, possibly only about 15minutes. From that stage the mixed liquor moves to a second anaerobiczone stage 213, which is shown as by flowing over a weir or baffle 216,although movement to the stage 218 could be other than over a weir.

Mixers 219 in the anaerobic stages allow mixing of the feed with thetank contents for further consumption of readily available soluble foodand conversion of colloidal and particulate food to a soluble form forconsumption by the microbes.

As noted above, only a selected portion of the RAS is introduced alongwith the incoming wastewater, at 212/150. The remainder of the RASportion passes through a line 220, to be introduced into the secondstage as illustrated. This is preferably via an appropriate form ofdistributer, e.g. a horizontal pipe 222 with multiple openings to evenlydistribute the RAS across the bottom width of the tank. With a portionof the RAS introduced farther downstream than the influent, theproportions of RAS at 212 and 220 can be adjusted so as to achieve ahigh F/M ratio, particularly in the first stage 215. In a preferredembodiment the F/M ratio is at least 5 in that first stage 215. Thismight be achieved using a recycle split with, for example, about 25% to40% (this could range from 10% to 50%) of the RAS introduced with theinfluent via the line 212 as a function of the influent wastewaterconditions. As note above, the retention time in the first stage isshort, no more than 30 minutes.

A third stage 224 is shown in the anaerobic zone in the illustratedembodiment, entering past a divider 225 which can be a weir as shown. Anarrow 226 indicates exit flow of MLSS from the third stage 224 and fromthe anaerobic zone. It should be understood that further anaerobic zonesor stages could be included downstream of that shown. Mixers 219preferably are provided in each stage. In the second and third stagesthe mixers are turned off periodically. Flow continues through thestages whether the mixers are on or off. In the first stage 215 it isimportant that all the microbes are in contact for consumption ofinfluent soluble good food at highest F/M ratio, and the mixer need notbe shut off. In the second and third stages 218 and 224, mixers areturned off for a selected period of time, greater than one hour, atdesired intervals. When the mixer is off heavier solids includinggranular sludge and unbiodegradable particulate food settle to thebottom of the tank, while the flow in and out of the tank continues tocarry lighter solids and smaller granules to the next tank. The solidsthat settle provide time for intimate contact between the fastersettling granular sludge and biodegradable particulate solids.

Under that condition the biodegradable solids from the influent arehydrolyzed, and the hydrolyzed products are fermented to provideadditional sbCOD for the granules. During this time the granules areconsuming the sbCOD at a deeper biofilm depth and have less competitionfor the food from flocculent sludge.

The consumed sbCOD (soluble biodegradable COD) in the anaerobic zone isstored as polyhydroxyalkanoates (PHAs) by the bacteria in the granules.During the subsequent mixing period these granules move to thedownstream anoxic and aerobic zones where the PHAs are oxidized toresult in the growth of new granules to increase the granular sludgebiomass content.

Larger granules in a granular/floc activated sludge system have highersettling velocities and thus may be more easily separated from the floc.The size of the granule can be affected by the bulk liquid solublebiodegradable COD (sbCOD) concentration in the anaerobic zone where theinfluent wastewater and return activated sludge containing granules arefirst in contact. A higher bulk liquid COD concentration results in agreater diffusion depth for sbCOD into the granule biofilm and thusprovides for growth at deeper depths leading to a larger granule. Theanaerobic zone in this innovative process design achieves providing ahigher sbCOD concentration for granular growth using two features in thefirst anaerobic stage in the anaerobic zone: 1) a relatively smallinitial volume in stage 1 to achieve a high soluble BOD loading in g/L-dor high F/M and 2) intimate contact between the granular sludge andparticulate BOD during the mixer-off operation.

Terms used herein such as “about” or “generally” should be understood asmeaning within 10% of the value stated.

The above described preferred embodiments are intended to illustrate theprinciples of the invention, but not to limit its scope. Otherembodiments and variations to these preferred embodiments will beapparent to those skilled in the art and may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

We claim:
 1. A wastewater treatment system including a series of biological process zones and a downstream clarifier, and further comprising: a sidestream flow from an aerobic process zone of the series of process zones and receiving a selected portion of sludge exiting the aerobic process zone, the sidestream flow including a sidestream separator for separating granular sludge from floc sludge to produce a first separator effluent containing primarily floc sludge, the sidestream separator having a second effluent enhanced in granular content, the sidestream separator further including a recycle stream of the first separator effluent, recycled back to the sidestream flow into the sidestream separator, with a control for controlling flow via the recycle stream, a portion of the first separator effluent being a waste stream, at least intermittently, and the second effluent from the sidestream separator joining with a main flow from the aerobic process zone to the clarifier, so that flow entering the clarifier contains an enhanced proportion of granular sludge thus enhancing settling rate in the clarifier, tending to collect a granular-rich sludge in a bottom area of the clarifier, whereby settling of sludge in the clarifier is enhanced to increase clarifier efficiency, and control of granular sludge and floc sludge content in the process stream can be enhanced by adjustments in the operation of the sidestream.
 2. The wastewater treatment system of claim 1, wherein the clarifier has a floc-rich region separated from the granular-rich sludge, and including a recycle line of floc sludge from the floc-rich region of the clarifier to at least one of the process zones.
 3. The wastewater treatment system of claim 2, wherein said one of the process zones is said aerobic process zone or an anoxic process zone.
 4. The wastewater treatment system of claim 2, including a recycle flow of granular biomass from the bottom of the clarifier to an anaerobic process zone of the series of biological process zones, with a portion of the settled granular sludge from the clarifier being wasted.
 5. The wastewater treatment system of claim 1, wherein the clarifier produces a clarified effluent, and the system includes a recycle of a portion of the clarified effluent to the sidestream separator for dilution of the flow into the separator.
 6. The wastewater treatment system of claim 1, wherein the sidestream flow from the aerobic process zone is from an upper level of the aerobic process zone, above the level of the main flow from the aerobic process zone.
 7. The wastewater treatment system of claim 1, further including a recycle line for the second effluent to an anaerobic zone of the series of process zones, for directing a portion of the second effluent to the anaerobic zone when desired.
 8. The wastewater treatment system of claim 1, wherein the clarifier includes a second separator positioned within the clarifier, and wherein the main flow from the aerobic process zone goes to the second separator, so that flow in the clarifier downstream of the second separator contains an enhanced proportion of granular sludge thus further enhancing settling rate in the clarifier, the second separator being effective to further separate granular sludge from floc sludge such that granular sludge settles more rapidly to the bottom of the clarifier, with primarily floc sludge from the second separator being directed to a radially outward region of the clarifier so as to settle in an annular area of floc sludge radially outward from settled granular sludge, and the system including a recycle line of floc sludge from the outer annular area of the clarifier to at least one of the process zones, and a recycle flow of granular biomass from the bottom of the clarifier to an anaerobic zone of the series of process zones, with a portion of the settled granular sludge from the clarifier being wasted, whereby settling of sludge in the clarifier is further enhanced to increase clarifier efficiency.
 9. The wastewater treatment system of claim 8, wherein the clarifier produces a clarified effluent, and the system includes a recycle of a portion of the clarified effluent to the sidestream separator for dilution of the sidestream flow into the sidestream separator.
 10. The wastewater treatment system of claim 8, wherein the clarifier has an inflow pipe receiving the main flow from the aerobic process zone, said second separator including an energy dissipating inlet connected to the inflow pipe and receiving sludge having both floc and granular biomass, the energy dissipating inlet having a bottom plate and internal baffles configured to direct sludge in generally even distribution radially outwardly into liquid volume of the clarifier, such that sludge solids settle by gravity to a clarifier tank floor sloped downwardly toward the center of the clarifier, with granular sludge settling faster than floc sludge and the floc sludge settling slower and more outwardly into said annular area of floc sludge, the second separator further including the clarifier having a granular sludge exit through the tank floor, near the center of the clarifier, for said recycle and wasting of settled granular sludge, and a floc sludge exit through the tank floor spaced outwardly from the granular sludge exit for said recycle line of floc sludge, and the second separator further including an annular sludge dividing deflector plate extending up from the tank floor and positioned radially inwardly from the floc sludge exit, so that floc sludge, which tends to settle more slowly and travel farther outwardly in the clarifier than granular sludge, tends to settle on the tank floor outwardly of the dividing deflector plate while the denser granular sludge tends to settle inwardly of the dividing deflector plate, whereby sludge exiting the granular sludge exit has a higher concentration of granular sludge than sludge exiting at the floc sludge exit of the clarifier.
 11. The wastewater treatment system of claim 10, wherein the clarifier has a rotating sludge removal arm positioned on and movable on the clarifier floor in a sweeping motion to bring settled granular sludge to the granular sludge exit, and including a floc sludge removal arm on the clarifier floor and movable in a sweeping motion to bring floc sludge to the floc sludge exit.
 12. The wastewater treatment system of claim 10, wherein the energy dissipating inlet is submerged and further including an upper deflector plate in an annular configuration above and outward from the energy dissipating inlet, positioned to deflect sludge emerging from the energy dissipating inlet away from a liquid surface in the clarifier and outwardly in the clarifier.
 13. The wastewater treatment system of claim 10, wherein the energy dissipating inlet has a downflow configuration, with the internal baffles further configured to direct floc biomass in generally even distribution radially outwardly and upwardly to exit a floc discharge opening into liquid volume of the clarifier and faucet baffles to direct granular biomass in generally even distribution radially inwardly and downwardly into the liquid volume.
 14. The wastewater treatment system of claim 1, acting as a main process for removing nitrogen and/or phosphorus, and additionally including a second sidestream flow comprising a sidestream treatment incubator system for generating granular biomass for use in the main process, comprising: a biological sludge process stream with one or a succession of incubator process zones, to remove nitrogen or nitrogen and phosphorus from activated sludge, with a continuous influent of solids processing reject water or influent wastewater into the incubator process zones, a first incubator zone of said incubator process zones being an anaerobic or anoxic zone, an incubator separator receiving sludge flow from the biological sludge incubator process zone(s), with sludge flowing through the incubator separator, in which granular sludge is separated from floc sludge, with granular-rich sludge collected in a bottom area of the incubator separator, a majority of the granular-rich sludge in the incubator separator being recycled to the first incubator zone so as to feed the granular biomass with influent soluble bCOD, and a portion of the granular-rich sludge being directed to the main process.
 15. The wastewater treatment process of claim 14, wherein the incubator separator has a primarily floc sludge overflow, separate from the granular-rich sludge, the primarily floc sludge overflow being directed to the mainstream process.
 16. The wastewater treatment system of claim 15, wherein the primarily floc sludge overflow is directed to the clarifier of the mainstream process.
 17. The wastewater treatment system of claim 14, wherein said portion of the granular-rich sludge is directed to an anaerobic zone of the series of biological process zones of the mainstream process.
 18. The wastewater treatment system of claim 1, with continuous flow of wastewater through the series of biological process zones, a first of the biological process zones being an anaerobic zone for encouraging selective growth of granular biomass, the anaerobic zone comprising: at least two successive stages in the anaerobic zone, including a first stage and a second stage, a continuous flow of influent wastewater to the first stage of the anaerobic zone, a recycle into the continuous flow of influent wastewater, the recycle comprising a first portion of a recycled activated sludge (RAS) stream from a downstream process zone of the series of biological process zones to produce a continuous combined raw influent/RAS flow into the first stage, the first stage being of limited volume, and dwell time in the first stage being no greater than 30 minutes, so as to provide for intimate contact between the incoming wastewater, rich in food, and the RAS, rich in biological activity, such that granular biomass present in the RAS is exposed to the food of the incoming wastewater for consumption and storage leading to growth of granules in further non-anaerobic zones, a mixer in the first stage to mix the RAS and incoming wastewater to provide a mixed liquor, a continuous flow of the mixed liquor from the first stage to the second stage, a flow of a second, remaining portion of the RAS into a bottom region of the second stage to mix with the mixed liquor in the second stage, a mixer intermittently operated in the second stage such that mixing of the incoming RAS and sludge from the first stage occurs intermittently whereby when the mixer is off heavier granular biomass tends to settle deeper than floc biomass in the second stage, so that said remaining portion of RAS entering the second stage comes into intimate contact with the settled granular biomass and particulate BOD, and the proportions of incoming wastewater and RAS in the first stage being such as to create a food to mass ratio (F/M) of at least
 5. 19. The wastewater treatment system of claim 18, wherein the second stage includes a distributor introducing the second, remaining portion of RAS into the second stage, to distribute the incoming RAS essentially uniformly across the width of the second stage and at said bottom region of the second stage.
 20. The wastewater treatment system of claim 18, including a third stage downstream of the second stage, mixed liquor being moved continuously from the second stage to the third stage.
 21. The wastewater treatment system of claim 18, wherein at least said aerobic process zone is positioned downstream of the anaerobic zone, said sidestream separator being downstream of the aerobic zone, and the clarifier being connected to the sidestream separator such that the clarifier tends to concentrate granular-rich sludge in a bottom area of the clarifier, with at least a portion of the granular-rich sludge being directed back to the first stage of the anaerobic zone as said RAS.
 22. The wastewater treatment system of claim 21, wherein the series of biological process zones includes an anoxic zone between the anaerobic and aerobic zones.
 23. The wastewater treatment system of claim 18, wherein said first portion of the RAS is 10% to 50% of the RAS.
 24. The wastewater treatment system of claim 18, wherein said first portion of the RAS is 25% to 40% of the RAS. 